German Foreign Minister Sigmar Gabriel attends a news conference after a meeting with his Russian counterpart Sergei Lavrov in Moscow, Russia, March 9, 2017. REUTERS/Sergei Karpukhin

BERLIN (Reuters) - German Foreign Minister Sigmar Gabriel questioned how Turkish President Tayyip Erdogan would know that an arrested German-Turkish journalist was a spy before he went on trial.

Relations between Ankara and Berlin have been strained in recent weeks after Deniz Yucel, a journalist for German newspaper Die Welt, was arrested in Ankara last month. In addition bans on planned rallies by Turkish ministers in Germany to drum up support for Erdogan have also caused anger.

"If Turkey really is a state under the rule of law as Mr Erdogan claims, I ask myself how he already knows and can say before the start of a trial that Deniz Yucel is a terrorist and a spy," Gabriel told German magazine Der Spiegel in an interview that will be published on Saturday.

Berlin says Turkey's claim that Yucel was working as a German spy is "absolutely baseless".

Der Spiegel reported that Turkish Prime Minister Binali Yildirim had promised German Chancellor Angela Merkel consular access to Yucel in a telephone call on March 4 but Ankara had not followed up on the promise.

"It would be disappointing if we could no longer rely on the Turkish prime minister's word," Gabriel said.

Yucel was arrested last month on charges of propaganda in support of a terrorist organization and inciting the public to violence.

The 43-year-old, the first German reporter to be held in a widespread crackdown that has followed the failed July 15 coup in Turkey, was jailed pending trial.